The increasing use of engineered nanomaterials in industrial and consumer applications has raised serious concerns about their environment health safety (EH&S). A particular concern is for occupational exposure to raw materials in the form of highly dispersed spherical and fiber- like shapes. Researchers seek to quantify nanomaterial interactions with biological systems and to develop predictive models of nanoparticle EH&S risk. However, limitations imposed by the model systems employed, the lack of NP standards, the failure of researchers to quantify or report the physiochemical properties of the NP investigated, and the inadequate availability of sensitive analytical instrumentation, have collectively hampered progress in attaining these EH&S goals. In the proposed project we seek to overcome limitations in detecting nanoparticles by developing a set of reagents (NProbes) that will enhance their presence in biological tissues that due to their size may be obscured from detection by other means. NProbe reagents will function in a similar fashion to those used to detect and quantify proteins in standard immunohistological analysis. NProbes with high binding affinity to both raw NP and transformed nanomaterials will be generated using protein-based (antibody and fibronectin) phage display technology. Nanomaterials of interest include carbon nanotubes, metal oxides, metals, and semiconductors. We will validate the binding of NProbes to raw nanomaterials and test their cross reactivity to samples of related and dissimilar composition. NProbe binding to nanomaterials transformed by penetration through skin will be also be demonstrated. We believe that NProbe reagents will be useful to researchers assessing nanoparticles tissue interactions in all mammalian, vertebrate, invertebrates systems as well as detection of nanoparticles in the environment. Successfully development of NProbe reagents will have a transformative effect on nanoparticle risk assessment research.